Yang Li --- some information on the net for your friend with Crohn's
disease:
Here's a page that I found with information; it's a good site to look around
from:
http://qurlyjoe.bu.edu/cduchome.html
This also looks like a good site:
http://www.ccfa.org/ - lots of stuff on this site, general info., standard
medical tests, treatments, alternative treatments, etc.
A friend of mine has Crohns disease, too. Best of luck.